This invention relates to a cleaning apparatus for a mirror which removes water drops, frost and ices on the mirror. This invention, for example, can be used in the environment of automobile back mirrors.
Japanese Utility-Model Laid-Open Patent Publication No. 61-30552 published on Feb. 24, 1986, discloses a conventional cleaning apparatus for a mirror. Referring to FIG. 6, the conventional apparatus is explained. A back mirror (32) is externally fixed to an automobile body. The back mirror (32) comprises a glass mirror (31), a stay (33) for supporting the glass mirror (31), an ultrasonic vibrator (34), an oscillating circuit (36), and a power switch (35) and a power supplier (37).
The power switch (35) is positioned in a compartment of the automobile. When the power switch (35) is turned on, the oscillating circuit (36) starts supplying an oscillating, signal and, the mirror (31) is vibrated by the ultrasonic vibrator (34). The ultrasonic vibration on the mirror (31) serves to remove water drops.
On the other hand, Japanese Laid-Open Patent No. 60-193739 published on Oct. 2, 1985, discloses another other conventional apparatus which removes water drops from the mirror by use of a Joule's heater. Such conventional apparatus comprises a metal film for reflecting light and a pair of electrodes allowing flow of an electric current through the film.
When the electric current flows through the film, the film generates a Joule's heat and this heat is conducted to the mirror. When the mirror is heated, the water drops are removed by evaporation.
However, the conventional apparatus with an ultrasonic vibrator cannot effectively remove frost and ice from the mirror because only a local position near the vibrator is heated, while a circumference part of the mirror is not heated.
Further, the conventional apparatus with a Joule's heater can hardly remove the water drops quickly as possible because the water drops are hard to heat rapidly by the conduction.